Semiconductor manufacture utilizes well known processes wherein multiple layers of various material, including semiconductor, insulator, and conductor layers, are selectively deposited and selectively removed using various deposition and material removing processes. One of those processes is used to create conductive traces to interconnect devices on the substrate. A plurality of electrically conductive traces is formed by photolithographic techniques.
One exemplary photolithographic technique involves forming a conformal layer of electrically conductive material over the dielectric layer and applying a photoresist layer over the electrically conductive material layer. The photoresist layer is photoactive, such that when exposed to light (usually ultraviolet light), the photoresist becomes insoluble (negative photoresist) in specific solvents. Light is projected through a template that shields specific areas of the photoresist while exposing other areas, thereby translating the pattern of the template onto the photoresist. After exposure, an appropriate solvent removes the desired portions of the photoresist. The remaining photoresist becomes a mask that remains on the electrically conductive material layer. The mask is used to expose areas of the electrically conductive material layer to be etched away while protecting the electrically conductive material that ultimately forms the electrically conductive traces.
A similar process is currently being used to provide conductive traces on a layer of ferroelectric polymer overlying a first conductive layer. FIG. 1 is a side view of a substrate 1 undergoing the process of adding conductive layer 20 to a conductive polymer layer 18, which itself is on the ferroelectric polymer layer 16. The substrate 1 comprises a basic lay-up of silicon 10, silicon dioxide 12, a first conductive layer 14, and a ferroelectric polymer layer 16. The substrate 1 has undergone application of a conductive polymer layer 18 and a conductive layer 20, upon which is a photoresist 22, wherein lithographic patterning, photoresist development, and plasma etching of the unwanted portions of the conductive layer 20 and conductive polymer layer 18. Plasma etching is a desirable means for removal of the conductive layer 20 and conductive layer 18 as it permits high resolution of the features.
FIG. 2 is a side view of the substrate 1 after removal of the photoresist 22. Removal of the photoresist 22 from the desired portions of the conductive layer 20 is done using a chemical removal process. Photoresist 22 exposed to plasma etching becomes hardened and difficult to remove. Strong chemicals are used in a process of dissolving away the photoresist 22 to expose the conductive layer 20. During the removal process, the chemicals also attack the desired conductive layer 20. This process leads to a high product defect rate. Further, the process is costly, and exposes the environment to a hazardous material that must be handled and disposed of properly.
Improved methods are needed to remove photoresist material that has been exposed to a plasma etching process. The methods must have a low defect rate, not harm the underlying desired material layers, be reasonably economical, and not present a hazard to personnel and the environment.